Cathode active material, method for manufacturing same, and lithium secondary battery comprising same

Abstract

A method for manufacturing a positive active material is provided. The method includes forming a positive active material precursor including nickel, mixing and firing the positive active material precursor and lithium salt to form a preliminary positive active material particle, forming a coating material including fluorine on the preliminary positive active material particle by dry-mixing the preliminary positive active material particle with a coating source including fluorine, and manufacturing a positive active material particle by thermally treating the preliminary positive active material particle on which the coating material is formed.

What is claimed is: 
     
       1. A positive active material including a positive active material particle containing lithium, a transition metal, fluorine (F), and oxygen,
 wherein the fluorine is provided on a surface of the positive active material particle and an inner portion of the positive active material particle, 
 the fluorine provided on the surface of the positive active material particle includes a coating material containing LiF, and is provided in a form of a layer or a particle on the surface of the positive active material particle, 
 a content of the fluorine provided in the inner portion of the positive active material particle gradually decreases in at least a part of the inner portion of the positive active material particle, 
 the transition metal contains 60 mol % or more of nickel, and 
 the fluorine (F) is provided to the positive active material particle by dry-mixing using a fluorine source containing NH 4 F or NH 4 HF 2 . 
 
     
     
       2. The positive active material of  claim 1 , wherein the positive active material particle contains lithium, a transition metal, fluorine (F), and oxygen, and
 the positive active material particle contains LiOH and Li 2 CO 3  as surface residual lithium, and the amount of Li 2 CO 3  is smaller than the amount of LiOH. 
 
     
     
       3. The positive active material of  claim 1 , wherein the transition metal further includes at least one of cobalt, manganese, and aluminum. 
     
     
       4. The positive active material of  claim 1 , wherein a concentration of the transition metal is constant in the inner portion of the positive active material particle. 
     
     
       5. The positive active material of  claim 1 , wherein the transition metal has a concentration gradient in the inner portion of the positive active material particle.